Hormones and the circadian rhythm were the major points of interest in this study. The researchers sampled the melatonin and catecholamine levels of advanced track athletes. These hormones play an important role in the circadian rhythm over the course of each day (the word circadian means "approximately a day").

Melatonin is the primary hormone controlling your daily sleep cycle. It’s responsible in large part for quality sleep, and its natural ebbs and flows are what make you sleepy at night and awake in the morning. It also happens to be a potent antioxidant, and chronic deficiency is bad for your health. This is one major reason you need a good night's sleep every night.

As important as melatonin is for sleep patterns, it also alters your body temperature, alertness, and excitability, so you don't want high levels while you’re exercising. Unfortunately, for athletes who work out early in the morning, this effect may be unavoidable. For this reason, the researchers also looked at catecholamines like adrenaline, which have the opposite effect of melatonin.

The researchers discovered that morning melatonin concentrations did indeed affect athleticism negatively, but these effects were counteracted by adrenaline. In other words, although higher melatonin in the morning reduced performance, adrenaline levels were also higher in the morning. The result was that the degree of wakefulness only impacted two qualities significantly: quickness and accuracy. As long as adrenaline was high, strength and power were unaffected.

For morning workouts, the researchers recommended that coaches and athletes focus on maintaining a positive atmosphere with more encouragement than usual. This approach will help ensure energy levels are sufficient to stimulate adrenaline and keep strength and power high.

However, this adrenaline effect won’t keep quickness and accuracy high, so quick motions like ladder drills and complex motions like Olympic lifts might be best to avoid in the early morning. In the study, the test of complex and quick foot motions revealed the athletes were slower in the morning and also made more errors. The researchers speculated that these effects should be over by 9:00am for most people, but prior to that, keep your training simple.